1. Field of the Invention
The present invention relates to a method of drying a substrate by blowing a gas onto the substrate and a method of manufacturing an image display apparatus, and particularly relates to a method of drying a substrate with the use of an air knife.
2. Description of the Related Art
A circuit pattern and the like on a glass substrate are formed by a resist film, in an image display apparatus such as a flat panel display. After the resist film has been formed, it is necessary to subject the resist film to chemical liquid treatment such as development, rinse the substrate by using rinsing water (pure water) after the chemical liquid treatment, and then dry the substrate.
A series of treatments for the substrate, which include the chemical liquid treatment, the rinsing and the drying, are usually conducted while the substrate is moved by a moving unit such as a roller conveyor, in one chamber.
Japanese Patent Application Laid-Open No. 2003-133217 discloses that an air knife is generally used for drying a substrate, drying air is simultaneously blown onto the upper surface and the lower surface of the substrate by the air knives, thereby rinsing water is blown off and removed from the surface of the substrate, the air knives are formed of a pair of upper one and lower one, and the arrangement of the air knives and the flow rate of air should be strictly vertically symmetric. In the above described series of treatments, the substrate is placed so that the surface having the resist pattern formed thereon becomes the upper surface.
It is known that when the substrate is dried, if the drying air is too strongly blown onto the upper surface of the substrate, the destruction of a resist pattern occurs, and Japanese Patent Application Laid-Open No. 2007-149987 discloses a technology of blowing drying air and then blowing hot air onto the substrate to finish drying so as to prevent the destruction of the resist pattern. Japanese Patent Application Laid-Open No. 2007-144314 discloses a technology of drying a substrate with a small amount of air, by devising a shape of a nozzle.
The above described destruction phenomenon of the resist pattern will be described below with reference to the drawings. FIGS. 10A and 10B schematically illustrate a state of the destruction of the resist pattern, which occurs when the drying air is blown onto the substrate by using the air knife. FIG. 10A is a plan view of the substrate, which is viewed from the upper side of the substrate, and FIG. 10B is a side view of the substrate, which is viewed from the transverse direction. The peeling of a resist-surface insolubilization layer 9 occurs in the same direction as that of the air supplied from the air knife, and a peeled portion 9a deposits on the resist pattern 8 to form a stripe shaped defect 10. The resist-surface insolubilization layer 9 means such a layer that the surface of an unexposed resist becomes insoluble in an aqueous solution of TMAH (tetramethylammonium hydroxide), due to an azo coupling reaction of the resin and a photosensitive agent caused by the contact of the surface of the unexposed resist with a developer such as the aqueous solution of TMAH. It is known that the resist-surface insolubilization layer 9 is generally formed so as to have a thickness of 50 to 200 nm from the surface of the resist 9b. 
It is known that the stripe shaped defect 10 occurs only in the end area 3 of the substrate, when the substrate passes through the air knife. Here, the end area 3 of the substrate means the range of approximately 10 to 20 mm by the distance measured from the end 21 in a head side of the upper surface (surface having resist pattern formed thereon) of the substrate. When an effective pattern region 22 exists in the end area 3, if such a defect occurs in the effective pattern region 22, the defect results in causing a decrease of the yield. Here, the effective pattern region 22 means a region in which the resist film with a fixed thickness is formed on the surface of the substrate and the pattern can be formed, and generally means a region in the inside from the end of the substrate by a fixed distance. The reason why the thickness of the resist film is not fixed in the outside of the effective pattern region 22 includes the influence of the surface tension in the end of the substrate when the resist is coated by a spin coating method, and the instability of a pumping operation in the starting time and finishing time of a coating operation when the resist is coated by a slit coating method.
The stripe shaped defect is formed by the collision of the mist of a rinsing liquid against the surface of the substrate, which has been formed when the end area 3 is dried by the air knife and has been passed by the drying air. It is hard for the methods described in Patent documents 2 and 3 to prevent the resist-surface insolubilization layer 9 in the end area 3 of the substrate from peeling and redepositing onto the resist pattern 8, and it is difficult for the methods to solve the above described problem.
An object of the present invention is to provide a method of drying a substrate, which can suppress the occurrence of the stripe shaped defect that is formed by the redeposition of the resist-surface insolubilization layer in the end area of the substrate, which has been peeled by a blown gas, and a method of manufacturing an image display apparatus.